The invention relates generally to multidrop telephone systems, and more particularly to multidrop digital loop telephone systems.
For over 20 years, Frequency Division Multiplexed (FDM) multidrop systems, such as the 82A, 84A, 85A, and CM-8 Station Carrier Systems have been used to deliver telephone service to remote areas. In these systems, analog signals are transmitted from a telephone company central office to a series of Remote Terminals (RTs) mounted on telephone poles. Telephone lines are then xe2x80x9cdropped xe2x80x9d from each RT to residences and businesses for use by customers. As with all analog systems, FDM multidrop systems are limited in their ability to handle the high data transfer rates required for such applications as high speed internet access or high speed fax transmission. Even when customers have an extra line dedicated for internet access or a fax machine, they often cannot use the extra line for its intended purpose due to interference problems associated with these analog systems. Modem digital phone systems solve the problems associated with transmitting data at high speeds over phone lines. However installation and configuration of these systems is often cumbersome. When a telephone technician installs a digital subscriber line (DSL) in an area, or adds a new phone connection in a location already having a DSL, he is often required to physically travel back and forth from the Remote Terminal (RT) to the central office, and also from RT to RT to verify that the system is working correctly. This can be extremely time consuming, especially in rural areas where the distance between RTs and the central office can be considerable. Furthermore, assigning phone numbers to the various RTs must be done manually at each RT Unit, which is also a time consuming process. If there are any mistakes in assigning the numbers, the technician must resolve them manually at the RT unit.
The present invention solves this problem using a multi-drop digital loop (MDDL) having a central office terminal and a series of remote terminals called xe2x80x9cAdd/Drop Units xe2x80x9d that communicate status and conflict information to one another over a telephone line using a full duplex 2B1Q encoding scheme. Each Add/Drop unit has a dedicated control channel through which it can send status messages to the central office terminal. The central office terminal can also use the control channel to send commands to each Add/Drop unit.
When in automatic assignment mode, the central office terminal transmits subscriber channels to each of the Add/Drop units. Each subscriber channel carries telephone communication to and from one of the phones on the loop.
In an alternative embodiment, the invention may be implemented as a central office terminal connected to an Add/Drop Unit, wherein the Add/Drop Unit drops a single digital subscriber line to a subscriber""s residence or business, and the single digital subscriber line feeds into a remote terminal. The remote terminal can then drop one or more telephone lines to the subscriber.